What does “water resistant for 80 minutes” mean on the new sunscreen packaging?

What does “water resistant for 80 minutes” mean on the new sunscreen packaging?

Zoe Diana Draelos, M.D.The new sunscreen labeling information instituted last summer is “water resistant for 80 minutes.” This means that the sunscreen has been tested to stay on the skin for 80 minutes when in contact with water. This testing is done in several laboratories around the US where the facility contains numerous indoor whirlpool tubs. Volunteers, usually college students, have their minimal erythemal dose (MED) determined and then have the sunscreen applied to a spot on the back. The volunteers then are exposed to 2MED of solar simulated radiation after sitting in the whirlpool for 80 minutes to be sure that the sunscreen still provides the desired protection. Since the term waterproof can no longer be used, “water resistant for 80 minutes” is the strongest claim that can be made to indicate that the sunscreen will stay on in water. The claim “water resistant for 40 minutes” can also be used to indicate products that have less water resistant properties.